1. Field of the Invention
The present invention relates in general to a belt-type continuously variable transmissions, and more particularly to metal V-belts used by such continuously variable transmissions. More specifically, the present invention is concerned with improvements through which a torque transmission efficiency of the belt is increased.
2. Description of the Related Art
Hitherto, various metal V-belts have been proposed and put into practical use in the field of wheeled motor vehicles that employ the belt-type continuously variable transmissions.
One of them is the metal V-belt disclosed in Japanese Laid-open Patent Application (tokkaihei) 10-213185. The metal V-belt disclosed in this published Application comprises a plurality of steel elements attached consecutively to two laminated steel bands. For such consecutive attaching, the steel elements have opposed grooves (or saddle grooves) that receive inside portions of the laminated steel bands respectively. Each steel element has at tapered flanks thereof, which are in contact with mutually opposed conical faces (or sheave surfaces) of drive and driven pulleys, a plurality of fine grooves. Due to provision of such fine grooves, lubrication oil is easily and effectively discharged in a circumferential direction of the pulleys.
The other one of the hitherto proposed metal V-belts is disclosed in Japanese Laid-open Patent Application (tokkai) 2005-321090. In this V-belt, there is provided means through which a frictional coefficient of the face of the belt in contact with the conical faces of a drive or driven pulley is improved. Actually, with such means, under operation of the transmission, there is effectively produced a protecting film of lubrication oil between flank surfaces of the steel elements and the conical faces of the drive and driven pulleys. Actually, the protecting film is composed of a torque transmission film that is adsorbed by additive components of lubrication oil and exhibits a shearing force and a lubrication film that serves as a lubricant. The flank surfaces of each steel element are formed with fine grooves by which supplied lubrication oil is appropriately discharged under operation of the transmission.